For conventional all-wheel drive (AWD) or 4×4 ESC systems, it is very difficult to identify low friction surfaces from surfaces with road slopes. Thus, it is difficult to identify low friction surfaces and downhill surfaces during traction control system (TCS) control. Even with the help from an accelerometer, it is very easy to falsely determine a slope on a low friction surfaces when wheels are slipping together with almost identical speeds. This will lead to incorrect estimated vehicle reference velocity. The conventional solution will normally require an AWD module to open a clutch or apply brake torque, distributed to the wheels, to try to slow down the over spinning wheels to correct the vehicle reference velocity. This conventional solution will introduce brake noise or uncomfortable engine control or switch the system from AWD to basically 2WD (with clutch open) on low friction surfaces.
In addition, conventional systems using sensors and algorithms detect the load for the entire vehicle. However, such systems do not detect if a part of the load is due to a trailer being towed and how this load is distributed. Therefore, it is not possible to optimize Electronic Braking System (EBS) functions for a specific driving situation.
Thus, there is a need for to provide a system that gives a more accurate vehicle reference velocity without need to open a clutch, thus providing more traction, and to provide a system that determines the vehicle load, particularly when a trailer is added to the vehicle, so as to optimize EBS functions for a specific driving situation.